Preparation And Properties Of Superhydrophobic Coating On Mg Alloy Surface

In recent years,superhydrophobic surfaces because of its unique superhydrophobicity and broad prospects for development,have become one of the focus of research at home and abroad.Magnesium alloy due to its low density,high specific strength characteristics,involving automotive,aerospace and biomedical and other fields.However,Magnesium alloys are susceptible to corrosion,thus limiting its further application.The construction of superhydrophobic coating on the magnesium alloy substrate effectively reduces the contact area between the corrosive medium and the substrate,which solves this problem.In this paper,magnesium alloy as the base,using two-step immersion method,chemical etching combined with solution dipping to form superhydrophobic surface.The morphology and composition of the prepared samples were analyzed by SEM,EDS,XRD,FT-IR and XPS.The wear and corrosion resistance of the prepared samples was measured by contact angle tester,simulated seawater immersion,friction and wear test,electrochemical test.The hierarcial flower like double layers superhydrophobic films is formed on the surface of magnesium alloy by two-step simple immersion method.The double layer is more dense and rough than the single layer.The as-prepared surface with a static water contact angle was measured to be 160° and the superhydrophobicity can be maintained for three months.The corrosion current density of the double-layer superhydrophobic film was decreased by two and one order of magnitude compared with that of the single-layer and uncoated magnesium alloy after immersion in the 3.5wt% NaCl solution for 6h.The rhombic-dodecahedral zeolitic imidazolate framework superhydrophobic film was prepared on the surface of magnesium alloy by chemical etching and dip-coating methods.Nanoparticles with diamond dodecahedron structure were adsorbed by physical adsorption in the microstructure produced by chemical etching,Increase the adhesion of the film to the substrate.And the daily contact angle of droplets on its surface is still greater than 150 °.It was found that the magnesium alloy covered by the superhydrophobic coating had obvious wear resistance by the friction and wear test.The impedance modulus of the superhydrophobic coating was higher than that of the untreated magnesium alloy by electrochemical workstation test,indicating the formed sample has good corrosion resistance.Based on the magnesium alloy,a flower like cerium conversion film was grown on the surface of the magnesium alloy,and then the superhydrophobic film was prepared on the surface by dip-coating method,which was equivalent to the double protective substrate.The prepared samples were placed in low temperature environment for different time,and it was proved that the superhydrophobic surface could effectively prolong the freezing time of the droplets and had good anti-icing performance.Through the friction and wear test,it was found that the superhydrophobic film had a smaller coefficient of friction and less wear.Through the electrochemical impedance test,it was found that the superhydrophobic layer still had a larger impedance modulus after soaking in seawater for several days.